gear

a part, as a disk, wheel, or section of a shaft, having cut teeth of such form, size, and spacing that they mesh with teeth in another part to transmit or receive force and motion.

an assembly of such parts.

one of several possible arrangements of such parts in a mechanism, as an automobile transmission, for affording different relations of torque and speed between the driving and the driven machinery, or for permitting the driven machinery to run in either direction:

first gear; reverse gear.

a mechanism or group of parts performing one function or serving one purpose in a complex machine:

steering gear.

2.

implements, tools, or apparatus, especially as used for a particular occupation or activity; paraphernalia:

fishing gear.

3.

a harness, especially of horses.

4.

Nautical.

the lines, tackles, etc., of a particular sail or spar.

the personal tools, clothing, and other possessions of a sailor.

5.

portable items of personal property, including clothing; possessions:

The campers keep all their gear in footlockers.

6.

wearing apparel; clothing:

The fashion pages of the Sunday paper are featuring the latest fall gear.

A wheel with teeth around its rim that mesh with the teeth of another wheel to transmit motion. Gears are used to transmit power (as in a car transmission) or change the direction of motion in a mechanism (as in a differential axle). Fixed ratios of speed in various parts of a machine is often established by the arrangement of gears.